If cost were not an option what would you prefer to use as an electrode? I have heard people talk of SS, Titanium, Nickel and Platinum. We currently use Ti on the cathode and MMO (exact specs are private due to patent pending status) coated Ti on the anode.

So forgetting cost which material is best for our situation?

Also is it possible to use a lesser base material (say copper) and have it coated in the value metal.

Obvious points needing to be addressed with the electrodes are oxidation protection at the anode and corrosive resiatance at the cathode.

You're above my pay grade with those materials. I've just been using 316L SS. I've heard good things about the Ti and MMO. But I've been trying to manufacture an affordable product for folks, and those materials don't lend themselves to making an affordable cell.

Hopefully some others here have experience with the more exotic materials.

I understand the issue of trying to keep it affordable but in essence we want a cell to perform at its most efficient and if that requires a more exotic metal then so be in my opinion....bulk buying will get the prices down in our case so I am not primarily concerned with that.

I really want to get a handle on which material is better and why?

We have found that conductivity of SS and Ti is not great....Nickel slightly better but Platinum is fantastic. Is there another reason as to choice of metal on the electrode?

The only 2 factors that I'm aware of is conductivity and corrosion resistance. I'm not sure how important conductivity actually is, as long as it's conductive enough. Just by adding a pinch more electrolyte you'll make up for the SS's shortfall in conductivity - thus maintaining the current you want.

It's possible that the resistance of the material would cause for less HHO production out at the edges of the plate - perhaps.

But that's all that I can see that would conceivably bear on the situation. Any material you're likely to use will be able to handle the temps. Depending on your cell design, and also with coated plates, modulus of expansion/contraction may be an issue.

But corrosion resistance is the biggest issue. Even 316L stainless eventually corrodes through.